On the biochemical background of cysteamine-induced duodenal ulceration in the rat.

In cysteamine-induced duodenal ulceration the endogenous prostacyclin level initially showed an elevation. This elevation later disappeared, and the endogenous prostacyclin level dropped to zero--that is, below the detection limit. During ulceration the mucosal DNA level decreased, a phenomenon that was directly proportional to ulceration. In the course of the ulcerative process in the duodenal mucosa a de novo protein synthesis took place. This process was most probably a mucus secretion and served as a protective reaction against damaging noxae. The mucosal cyclic adenosine 5'-monophosphate (cAMP) content increased in the so-called pre-ulcerative phase but later returned to the normal (physiologic) level. The changes in the cyclic guanosine 5'-monophosphate (cGMP) level were more pronounced than those of cAMP, and the final result was a decrease in the mucosal cAMP/cGMP ratio. In accordance with our previous results we conclude that a positive cAMP/cGMP 'shift' indicates antiulcerogenic, cytoprotective, reparative processes in the mucosa, whereas its decrease is connected to damaging noxae.